Essence for the senses

Vanilla. It's one of the most used spices in the world. It's also one of the most expensive.

Next to saffron and cardamom, it's the world's third-priciest spice. Which begs the question: can you grow it yourself? Well, yes, you can, but you need to be awfully dedicated to its success.

Vanilla (Vanilla planifolia) is a tropical orchid (the only fruit- bearing member of the orchid family), and as such needs tropical conditions (you can mimic that in a hothouse if you have one). In its natural habitat in Mexico, pollination is completed by native bees and hummingbirds, both of which are able to penetrate the tough membranes of the flowers. As each flower is open for less than a day, albeit during a two-month period, there's only a small window of opportunity for pollination. If the flowers don't get pollinated, they wilt and fall within hours of opening.

You may have noticed that we don't have hummingbirds in New Zealand. Nor do we have native Mexican bees. Which means to acquire fruit on your vanilla plant in this part of the world, you need to hand pollinate it. Thanks to Edmond Albius, a slave on the French island of Reunion, we know just how to do that. It was he, in 1841, at the age of 12, who perfected the art of hand- pollinating vanilla. Until then, growers who transplanted vanilla outside its natural homeland were stumped as to why the plants failed to set fruit. Albius used a small stick to lift the flowers' membranes and smear the pollen with his thumb. That particular method is still used today - and so you too can copy it.

That's all very well, but unless you provide your plants with conditions that mimic their natural habitat, you won't get very far.

"Heat and humidity are the two key things, because vanilla grows within 30 degrees either side of the equator," says Jennifer Boggiss of Heilala Vanilla, who, together with her husband Garth, are New Zealand's first commercial vanilla growers.

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Optimum daytime temperatures for cultivation are 15-30'C and nighttime temperatures 15-20'C, with humidity around 80 percent. Shading must also be around 50 percent. You can buy various shade cloths from horticultural suppliers with varying degrees of shade.

Soil should be loose and free- draining with a loamy texture and plenty of organic matter added in. A mulch is also recommended to help prevent the fine surface roots from drying out. Organic fertiliser is ideal. Jennifer says they use a liquid seaweed fertiliser for their plants. Though you could also use an orchid fertiliser.

A climbing vine that grows on a host plant in the wild, vanilla, in cultivation, needs some sort of support, because the vines are fast growers.

"It's a warm-growing vine that climbs all over the place," says Ross Tucker of Tuckers Orchids in Auckland. "Grown in glasshouses or conservatories, the vines can go up many metres, maybe 20m. They grow quite quickly in spring and summer. They can grow a couple of feet a day." In their native habitat, they can grow a staggering 90m.

But they won't start producing beans until plants are about 3 years old. About nine months after the flowers have been pollinated (funnily enough), the vanilla pods are ready for picking. They're harvested when the green pods begin to turn yellow. Then starts the curing process.

"That's where the quality comes in," says Jennifer. "The actual bean on the plant doesn't have any aroma. It's a bit like wine where it's developed over time."

Traditionally, the green beans are dipped into hot water (65degC) for three minutes to kill them and stop further vegetative development, and to kickstart the enzymatic reactions responsible for the production of aroma and flavour. They're then dried in the sun during the day and, before the heat is lost, wrapped up and placed indoors in insulated containers at night. They're usually dried during a six-week period, says Jennifer, in which time they turn a dark brown-black and lose up to five times their original weight when first picked.

So you see, you can grow your own vanilla, but it's a mighty long-winded process. But if you have a sunny conservatory or heated greenhouse (though your plant must not be in direct sunlight), why not give it a go? Provide some humidity in the form of regular misting (or maybe you have a very warm bathroom in which to place your plant), and you're good as gold. If you could manage to produce your own vanilla beans, it could be well worth it. You might be able to test its pre-Columbian reputation as an aphrodisiac. At the very least you can skite to your friends and family that you grow your own vanilla.